The invention relates to image composition methods, and in particular to composition methods for displaying high dynamic range images on standard low dynamic range device.
Image reproduction is an important issue for artists in various Ages, such as painters or photographers. One goal of image reproduction is to reproduce original images based on image factors, such as brightness, colors, or figures. For image reproduction, low dynamic range (LDR) images are easy to reproduce, while high dynamic range (HDR) images are difficult.
The dynamic range of a scene is defined by the contrast ratio between its brightest and darkest parts. A high dynamic range image (HDR image) is typically generated by combining multiple LDR images of the same scene taken at different exposure levels. For example, a flat plate in a luminous room may compose a LDR image, while a black dog in white snow forms a HDR image.
Generally, painters can reproduce images properly through painting techniques even if the contrast ratio of an image is large. For traditional photographers, because of limitations of camera mechanism, the only recourse is to wait for a suitable time and scene for capturing images.
Recently, cameras have been digitized. Thus, the images taken by digital cameras are digital images. Digital photographers can post-process digital images via digital image processing methods to reproduce original images properly. Thus, HDR images can be composed and processed by some image processing tools to obtain a displayable low dynamic range image. However, present image composition tools cannot produce a satisfactory HDR image, especially eliminating the motion defect of the image, such as waterfalls, moving people, etc. Thus, more effective HDR image processing methods for image composition are desirable.